Ford F-650 2001 Owner's Manual page 182

Maintenance and care
Tire inflation pressure must not exceed the recommendations of
the axle, tire and/or wheel rim manufacturer for the specific
load, speed and application. The inflation pressures on the tire sidewall
do not take the wheel rim capabilities into consideration.
Never use a rim of different manufacture or any different size or
type than original rims.
Try to replace tires in pairs on the same axle shaft. Tires larger or
smaller than originally installed may affect the accuracy of the
speedometer. Consult your dealer about the need to change the switch
setting on the back of the speedometer.
Front wheel alignment
If abnormal tire wear or ride and handling characteristics such as vehicle
lead or wander are experienced with properly inflated tires, the front
end alignment should be checked.
Wheel bearing care
Front and rear wheel bearings are adjustable to correct for bearing and
spindle wear. Long bearing life depends upon proper adjustment and
correct lubrication. If bearings are adjusted too tightly (preloaded) they
will overheat and wear rapidly. Loose adjustment will cause pounding
and will contribute to uneven tire wear, steering difficulties and
inefficient brake operation.
Refer to the Ford Service Manual applicable to your vehicle for proper
tightening procedures and torque specifications.
Periodically check the oil level on oil filled front bearing hubs. If
necessary, add oil through the filler plug so the oil level is between the
ADD and FULL marks indicated on the hub. Do not overfill. Overfilling
can result in oil on brake linings.
Refer to your Scheduled Maintenance Guide for fluid level checks and
change intervals for the front hubs.
Your front hubs may be filled with an optional synthetic fluid which
allows use of the extended service intervals. A green colored filler plug
identifies use of the synthetic fluid.
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